stringToTimestamp

Converts a string in JDBC timestamp escape format to a Timestamp object.
To be precise, we prefer to find a JDBC escape type sequence in the format
"yyyy-mm-dd hh:mm:ss.fffffffff", but this does accept other separators
of fields, so as long as the numbers are in the order
year, month, day, hour, minute, second then we accept it.

Parameters:

s - Timestamp string

cal - The Calendar to use for conversion

Returns:

Corresponding java.sql.Timestamp value.

Throws:

java.lang.IllegalArgumentException - Thrown if the format of the
String is invalid